Commonly, an artificial knee joint has a femur component that is to be fixed to a distal portion of a femur, and a tibia component that is to be fixed to a proximal portion of a tibia (e.g. see Patent Document 1). The femur component includes an arc-shaped femur sliding face. The femur sliding face can come into contact with a tibia sliding face, which is formed in the tibia component. The tibia sliding face is a concavely curved face that is recessed toward the tibia side. Bending motion of the knee is performed as a result of the femur sliding face sliding with respect to the tibia sliding face.